The present invention relates to a furnace for melting materials with low melting point, both metals or metallic alloys and synthetic materials, with improved casting duct.
Machines for forming parts by means of the centrifugal casting of metals or metallic alloys or synthetic materials with low melting point are known. These machines generally comprise a mold which is constituted by two flat elements made of vulcanized rubber which are mutually coupled at one of their respective faces and in which the forming cavities are defined.
The forming cavities are connected, by means of appropriate ducts defined in the two flat elements, to a central feed duct into which the molten material, which must fill the forming cavities, is poured. During the introduction of the molten material, the mold is rotated about the common axis of the two plates, which is generally vertical, so that the molten material fills the forming cavities, reproducing even the smallest details with extreme precision.
This type of machine can be supplied with molten material either manually or directly by means of a furnace which is arranged above the machine.
Furnaces currently intended for this use generally comprise a cylindrical body made of refractory material which surrounds a crucible intended to contain the molten material. Inside the body of the furnace, around the crucible, there are electric resistors or other sources of heating, for example gas- or gas oil-powered ones, for heating the crucible. The molten material is conveyed to the forming machine through a substantially vertical casting duct which is defined in the body of the furnace laterally to the crucible.
The casting duct has an inlet which is arranged above the level of the free surface of the molten material, which is fed to the casting duct by means of an extraction ladle which can move vertically in the crucible,
Said known types of melting furnaces have some problems.
In fact, the casting duct is generally defined in a region of the furnace which is not affected, except indirectly, by the electric resistors which heat the crucible, and thus the molten material, while traveling along the casting duct, can progressively cool until it obstructs the casting duct, requiring the intervention of an operator to restore the correct flow of material toward the forming machine.
In order to avoid as much as possible occlusions of the casting duct, the material is kept in the crucible at a temperature which is significantly higher than its melting point.
Although this solution is effective, it requires the use of particular alloys which are more expensive and increases the forming of slag in the molten material.